§1.1 Field of the Invention
The present invention generally concerns the design of an array of air plasma torches, which are spread into fan-shape to have larger exposure width. The plasma effluent produced by the device carries abundant atomic oxygen, which can effectively kill all kind microbes. Applications of the device include sterilization of carpets, clothes, and bed sheets, a dry approach and no chemical materials used.
§1.2 Background
Described in the article “Design and electrical characteristics of a modular plasma torch,” IEEE Trans. Plasma Sci., Vol. 27, no. 3, pp. 752-758, 1999; and in the U.S. Pat. No. 6,329,628 titled “Methods and Apparatus for Generating a Plasma Torch,” (“the '628 patent”) by S. P. Kuo, et al., an array of arc torches can be run simultaneously in low frequency (e.g., 60 Hz) periodic mode by a single power supply. In an array arrangement, the covered area of produced plasma can be enlarged considerably. A device employing an array of torches to generate plasma for the application of carpet sterilization is devised. The device spreads each torch, normally having a cylindrical shape, in the array to a fan-shape, so that the plasma effluent produced by the torch array covers an extended wide region. Moreover, this device produces low temperature non-equilibrium air plasma carrying abundant atomic oxygen, which can effectively kill all kind microorganisms including the toughest biological agents, bacterial spores, such as Anthrax (See, e.g., the articles: H. W. Herrmann et al., “Decontamination of chemical and biological warfare (CBW) agents using an atmospheric pressure plasma jet (APPJ),” Phys. Plasma, Vol. 6, pp. 2284-2289, 1999 (hereafter referred to as “the Herrmann article”); and Wilson Lai et al., “Decontamination of Biological Warfare Agents by a Microwave Plasma Torch”, Phys. Plasmas, Vol. 12, 023501 (1-6), February 2005 (hereafter referred to as “the Lai article”)). The plasma effluent has a large flow speed (>20 m/s) to penetrate through the carpet. Thus, this sterilizer kills microbes in the carpet as well as those accumulated behind the carpet.
The advantages of producing non-equilibrium plasma are 1) the plasma effluent is low temperature and thus does not burn the carpet and 2) having a better usage of the electron plasma energy, gained from the discharge, for the production of reactive oxygen species (ROS), rather than for heating the torch. ROS (particularly, the reactive atomic oxygen (RAO)) are the decontaminant.